In order to gain insight into the function and role of the opiate receptor subpopulations in the mediation of analgesia, addiction, euphoria and tolorence, we have prepared specific, irreversible inhibitors of these receptors based on the patent, nonrigid analgesics fentanyl and etonitazene. In these studies, we have obtained at least one compound which preferentially inhibits mu receptors and one which preferentially inhibits delta receptors.